For horizontal wells drilled with water based mud system, the bio-polymeric drilling fluid form a strong and nearly impermeable mud cake coating on the wellbore wall, removal of which is of utmost importance to restore the productivity or injectivity of the well. An enzyme and a weak acid system attacks the bio-polymers and carbonate bridging material of the cake, resulting degradation of the filtercake, though stability of such enzyme in presence of a weak acid or an acid precursor releasing weak acid, has been a problem area.
The present invention is directed toward overcoming one or more of the problems discussed above.